It takes Marjorie 5 seconds to paint each
watermelon seed on the plastic watermelon and
Pembroke 4 seconds to do the same. How many
seconds will it take the two of them together to
paint 171 watermelon seeds?

When Marjorie and Pembroke work together, they can combine their efforts. Marjorie takes 5 seconds per seed, which means she paints 1 seed in 5 seconds, or 0.2 seeds per second. Pembroke, on the other hand, paints 1 seed in 4 seconds, so he paints 0.25 seeds per second. Together, they can paint 0.2 + 0.25 = 0.45 seeds per second.

To find out how long it takes them to paint 171 seeds together, divide 171 seeds by the combined rate of 0.45 seeds per second:

171 ÷ 0.45 = 380 seconds.

So, it will take Marjorie and Pembroke 380 seconds to paint all 171 watermelon seeds together!